4 - Instrumentation of the root canal system Flashcards
What are the design objectives of instrumentation?
- continuously tapering funnel
- maintain apical foramen in original position
- keep apical opening as small as possible
What is meant by chemomechanical preparation of the canals?
Chemo
- irrigate to kill microorganisms
- removes smear layer
Mechanical
- prepare shape
- flush out
What is the estimated working length?
- estimated length at which instrumentation should be limited
- obtained by by measuring pre-operative radiograph from coronal reference point to radiographic apex then subtracting 1mm
What is the corrected working length?
- length at which instrumentation and obturation should be limited
- obtained using an electronic apex locator or a working length radiograph
What is the master apical file?
- the largest diameter file that is taken to working length
- the width of the apical preparation
What are the different movements used in instrumentation?
- filing
- reaming
- watch-winding
- balanced force motion
- envelope of motion
Describe watch winding.
- back and forward twists of 30-60 degrees
- light apical pressure
- effective when used with K files
Describe the balanced forced technique.
- file inserted into canal
- 1/4 turn CW with pressure, then 1/2 turn CCW with continuous pressure
- complete 2-3x then remove to assess debris and clean file
What is the irrigation protocol?
- EDTA 17% for 1 minute OR
- sodium hypochlorite 3% (30ml for 10mins)
How should you inject irrigation solution into the canal?
With finger, very slowly, do not use thumb
What is a barbed broach?
- tapered file that looks like barbed wire
- used for extirpating not enlarging canals, should be used to engage pulp tissue and remove it
- should not engage with canal walls
- v fragile
What does white indicate on the ISO colour code?
15 or 45
What does yellow indicate on the ISO colour code?
20 or 50
What does red indicate on the ISO colour code?
25 or 55
What does blue indicate on the ISO colour code?
30 or 60
